A spate of projectile vomiting in the AFC Wimbledon dressing room at the interval accounted for top-scorer Joe Piggott.
Bloodied and beaten following a first-half pummelling, fate intervened. Kindly, as it turned out.
Replacing the sick-stricken Piggott was James Hanson, the summer recruit possessing fine League One pedigree during his Bradford days, only still to register for the Wombles.
It was an enforced selection dictated by providence which proved inspired, transforming the match’s flow from the moment his 63rd-minute effort struck the net.
Suddenly a rampant Pompey, threatening a flurry of goals, traded silk for steel, retreating in numbers to barricade their under-siege penalty area.
Yet such is the supreme might of this Blues rearguard, even destiny cannot succeed in its persuasive decree.
The newly-administered substitute Hanson was unplayable at times, an effective attacking battering ram for team-mates reinvigorated in hope following his goal.
For approaching 30 minutes, Jackett’s troops had to dig in during preservation attempts to retain their lead. It was unrelenting and often uncomfortable to watch.
The fact that Craig MacGillivray barely had a save to make was testament to playing colleagues in front, assembling an outstanding shield during the stern examination.
A quirk of fortune commanded Hanson be ushered onto the pitch to wreak his danger, but ultimately not even that could break down this resolute and gutsy Blues outfit.
Time and again this season, Pompey have demonstrated their outstanding talent for retaining a lead. It’s a prized trait continuing to serve well.
Only injury to Nathan Thompson and Jack Whatmough has prompted changes to the back four plus MacGillivray during the opening 13 league fixtures, with Jackett creating a rock- solid unit.
Jamal Lowe and Ronan Curtis may be this campaign’s offensive stars, but defensively the Blues possess a spirited band of players capable of gritty displays.
Kingsmeadow, though, provided the setting for an admirable team display, with Tom Naylor outstanding in his customary holding-midfield role, particularly when required to scrap.
The former Burton man had opened the game’s scoring with a 23rd-minute header from Dion Donohue’s right-wing corner.
It represented his maiden Pompey goal in 15 appearances following a summer switch on a free transfer.
The outstandingly-mobile Naylor’s chief responsibility, though, remains to protect the back four, a task he can be relied to perform admirably when challenged to carry out.
During the Hanson-led onslaught, Jackett’s men required battlers, heart and grit – something they have in plentiful demand within their ranks.
Admittedly, too often the ball was hooked forward in blind desperation by a Blues side clinging on, struggling to retain possession and satisfied to temporarily remove the pressure.
It was a thankless task for strikers Oli Hawkins and then replacement Brett Pitman to pursue random balls pumped away from danger during such testing times.
Nonetheless, Pompey survived, even negotiating the unwanted surprise of five additional minutes without any further damage.
Quite a contrast to the opening hour in which Jackett’s men were at their brilliant best in attacking terms.
Both Naylor and Hawkins, when afterwards addressing the press, felt the game should have been settled at half-time, such was the Blues’ irresistible dominance.
They had headed in at the interval with a 2-0 lead yet, in truth, the advantage should have been far greater as the Wombles were swamped.
Even shortly before Hanson’s attempted rescue act, Jake Jervis had cleared Matt Clarke’s header off the line to prevent the visitors claiming an unassailable 3-0 lead.
The opening 45 minutes were arguably Pompey’s most impressive of the season, Jackett’s revamped side was full of pace, power and menace, with goal opportunities piling up.
Pompey’s boss was without Curtis on international duty, so made three changes to the team which suffered defeat to Gillingham in their previous league outing.
Ben Thompson replaced Ben Close in the centre of midfield, while Pitman was removed in favour of Hawkins’ differing striking style.
The final change was Dion Donohue handed his first league appearance of the campaign following a successful goalscoring comeback in the Checkatrade Trophy win against Crawley last Tuesday.
With Jamal Lowe pushed into a central role, at times the system looked to be two up front, with Donohue and Gareth Evans positioned out wide.
Of course, to cope with the pressures created by the subsequent 2-1 scoreline, that formation soon focused on defending and keeping the Wombles at bay by whatever means necessary.
Still, in the opening 10 minutes alone, home keeper Joe McDonnell had to twice save with his feet, firstly from Naylor’s header and then an Evans shot.
It was a taste of things to come, with Pompey pouring into the opposition half at will, suggesting they were capable of scoring with every attack.
They had their opener through Naylor and on 31 minutes doubled the advantage when Lowe fed the overlapping Lee Brown down the left.
The full-back managed to pull the ball back from the byline and, although Hawkins was unable to convert, the pass found Evans arriving at the back to apply a first-time angled finish.
Neal Ardley’s men couldn’t respond and would have been delighted for the half-time whistle.
Sure enough, three substitutes were brought on, despite the remaining players still in the changing room. As was later explained, Piggott’s sudden illness had caused turmoil.
Regardless, the game continued in the same flow. That was until Evans woefully mishit an attempted clearance with his left foot and Hanson pounced.
The striker’s superb first-time shot from outside the box found the net – turning the match on its head.
But Pompey valiantly withstood the barrage. A gutsy team display triumphed.